1. Field of the Invention
The present invention relates to a camera with a built-in magnetic recording and reproducing apparatus, which can record photographic information and developing treatment in a magnetic recording portion made of magnetic film or reproduce the recorded information.
2. Related Art Statement
In recent years, a camera with a built-in magnetic recording apparatus for recording photographic information or the like in a magnetic recording portion made of magnetic film has been proposed.
Several kinds of structure around the magnetic recording head used in the aforesaid magnetic recording apparatus have been proposed. For example, these apparatuses as disclosed in the official gazettes of Japanese Patent Laid Open Nos. 3-168624/1991, 3-289639/1991, and PCT application (International patent application) No. WO-90/04202 have the structure in which a magnetic head for magnetic recording and a pressure pad are arranged to sandwich film therebetween and face each other and the film is pressed on the magnetic head by the pressure pad at the time of recording.
A magnetic recording apparatus of a camera disclosed in the official gazette of Japanese Patent Laid Open No. 3-200130/1991 has the structure which drives a magnetic head to an operating position at the time of magnetic recording.
Nevertheless, an ordinary pressure pad made of ferrite material applied to the apparatuses disclosed in the aforesaid references has a defect in which the pad is easily worn away or becomes fuzzy by sliding a film end face or perforations into the pad. Further, a film's striking feature is hardening at low temperature in comparison with audio tape, so that the feature is disadvantageous for using the pressure pad. In addition, if film is sandwiched and supported in this way, the film transporting force will increase. Therefore, more electricity is used and especially, winding at low temperature becomes more difficult by increasing the film transporting force. As a matter of course, an electric battery is consumed faster.
Like a camera magnetic recording apparatus described in Japanese Patent Laid Open No. 3-200130/1991, a magnetic head is is moved, so that the reliability might be lowered by cutting a lead because an electric member is driven.
At the same time, in the aforesaid camera using photographic film having a magnetic recording medium of photographic information, a magnetic head whose shape has been used for a recorder is now used. The shape is approximately a rectangular parallelopiped and long in the optical axis direction. In the magnetic head shape, the front having a gap portion is formed as an arc surface bending in the film travelling direction.
The structure of a magnetic head which has been used will be explained as follows. In principle, a magnetic head is made of a ring-shaped iron core (hereinafter, core) and an operation coil wound on the core. The core is formed of magnetic materials including permalloy, ferrite and sendust. Required characteristics of the magnetic materials of the core include:
1) high magnetic permeability, PA1 2) high saturation magnetic flux density, PA1 3) small holding power, PA1 4) strong resistivity, and PA1 5) high hardness and good processability.
An operation coil is wound on a part of the core. The core and coil are stored in a shield case. Both ends of the operation coil are connected to a terminal, which is insulated and arranged in such a way that the terminal is projecting from the inside of the shield case to the outside, and further connected to an external circuit by its external projecting terminal. Additionally, the structure of the core is determined also in consideration of the efficiency of the magnetic circuit.
FIGS. 38(a)-38(d) show an assembly order of a magnetic head using a former ferrite core. A core 302 of a magnetic head 301 shown in FIG. 38(c) consists of a front core 303 shown in FIG. 38(a) and a back core 304 shown in FIG. 38(b). An operation coil 305 is wound on the back core 304 and then, a bonding surface 303a of the ground front core 303 and a bonding surface 304a of the ground back core 304 are bonded together to form a unitary structure as shown in FIG. 38(c).
At this moment, the bonding surfaces 303a and 304a stick together, so that an air gap between the bonding surfaces is decreased as small as possible. Then, these cores are stored in a shield case 301a as shown in FIG. 38(d) and the shield case 301a is filled with an adhesive agent or the like to seal the cores 302 in case 301a. However, the magnetic head 301 shown in FIG. 38 is composed, as a head, of two magnetic heads for recording and for reproducing, respectively.
FIG. 39 shows flow of magnetic flux in a core 308 of a magnetic head when information is magnetically recorded in a magnetic recording medium 307 on film 306 by a former magnetic head formed as stated above.
The core 308 is made of a strong magnetic substance, such as permalloy as stated above. When information current flows in an operation coil 309 wound on the core 308, magnetic flux .phi.c is generated and flows in the core 308 as shown by dotted lines. In a section of the core 308 to be magnetically recorded, a slit-like air gap portion 308a is formed. Actually, a thin metallic foil of non-magnetic substance is put in the air gap and fixed. Because magnetic resistance in a magnetic circuit is high in the air gap portion 308a of the core 308, the magnetic flux .phi.c which is flowing in the core flows by branching out into a magnetic flux route .phi.a spreading the outside of the core, a magnetic flux route .phi.b flowing across the air gap portion 308a, and magnetic flux .phi.e passing though the inside of the core. Among these branched magnetic flux, the magnetic recording medium 307 of the film 306 is magnetically recorded by the magnetic flux .phi.a. An important point in the design of the shape of the core is how much of the magnetic flux .phi.a is transmitted and how effectively the magnetic flux .phi.a is transmitted.
Therefore, the shape of the former core is approximately a square. However, in order to choose not only magnetic material of the core but also to reduce the cross-sectional area of the core for transmitting required magnetic flux and leak magnetic flux .phi.d which is not used for recording as small as possible, it is necessary to make a size D between facing parts of the core 308 long enough and to make a space enough for a coil wound on the core to increase the number of windings of the coil. Accordingly, it is unavoidable that a former core is formed into the aforesaid square shape and becomes longer in the optical axis direction lying at right angles to the travelling direction of the magnetic recording medium.
Further, film having a magnetic recording medium to be loaded in a camera is used. On the film, emulsion of silver salt is applied on a surface on a photographic lens side of base material formed of acetate or the like and a magnetic recording medium is applied on a surface of a pressure plate side at the back of the base material. Thus, in order to press and bring a magnetic recording and reproducing head into contact with a magnetic recording medium of film, it is necessary to arrange the head at the rear of film which is put on the side of a photographer of a camera. If a magnetic head having a former core of a square-shape is arranged on the rear of film of a camera, the camera has a defect of becoming thicker, having difficulty in gripping, and therefore, being hard to be operated.
Therefore, it can be proposed to make a magnetic head flat while the former square-shaped structure is used. FIG. 40 shows the structure of the flat-shaped magnetic head. FIG. 41 shows the outward appearance of a magnetic head 310 having the structure shown in FIG. 40.
A core 311 of the magnetic head 310 is formed of thin U-shaped cores having cross-sectional areas required for transmitting specified magnetic flux. A gap portion 311a required for magnetic recording is composed of a pair of the cores 311. An operation coil 312 is wound on each core. The core is stored in a shield case and fixed to the case as a unit by glue. The air gap portion 311a arranged at the center of the cores 311 is formed so as to be in contact with a magnetic recording medium 314 on film 313. An air gap portion 311b is formed on the opposite side of the air gap portion 311a of the core 311.
In the magnetic head 310 formed in this way, when information signal currents flow in the two coils 312 wound on the cores 311 to produce a magnetic field, most magnetic flux originated from the N Pole side of the coil flows in the core 311 as shown by the dotted flux lines .phi.c. Due to the high magnetic reluctance of the air gap portion 311a, the magnetic flux .phi.c flowing in the core is divided into a magnetic path of magnetic flux .phi.a going by a roundabout route like an arc on the side of the magnetic recording medium, a magnetic path of magnetic flux .phi.b approaching a surface that the core faces, and a magnetic path of magnetic flux .phi.e going by a roundabout route like an arc in the inside of the core in the air gap portion 311a. The aforesaid magnetic flux reaches the S Pole side of the coil. A magnetic recording medium is magnetically recorded by the magnetic flux .phi.a passing through the magnetic path on the side of the aforesaid magnetic recording medium within the magnetic path of the air gap portion.
Nevertheless, as shown in FIGS. 40 and 41, if a core is made to be flat, there is a problem in which not only the magnetic paths where the magnetic flux .phi.a, .phi.b, and .phi.e pass become larger but also the leak magnetic flux .phi.d becomes larger. The leak magnetic flux .phi.d returns to the coil before reaching the air gap portion 311a and is not used for magnetic recording in the magnetic recording medium. Therefore, the leak magnetic flux .phi.d remarkably lowers the magnetic head efficiency. The leak magnetic flux .phi.d becomes larger when a size D1 is made to be smaller an approach to the flux .phi.d.
As shown in FIG. 40, if the core of the magnetic head is changed to be a flat-shape while the core of the magnetic head has the former structure, the leak magnetic flux increases, so that problems are developed: specified characteristics cannot be obtained and a space for storing the coil cannot be secured.
A magnetic head needs positioning at the rear of film when the head is loaded in a camera. It is very important that a magnetic head is made to be a flat-shape (thin-shape) for providing a small camera.
As disclosed in the PCT application No. WO90/04202, it is known that a magnetic head is provided on film a pressure plate as a magnetic recording and reproducing head in a camera which uses photographic film with a magnetic information recording portion. As described in Japanese Patent Laid Open No. 3-200131/1991, it is known that a magnetic head is provided so as to be able to retreat against a magnetic information recording portion of film and brought into contact with the magnetic information recording portion only when information is recorded and reproduced.
However, in the magnetic head disclosed in the PCT application No. WO90/04202, a part of the magnetic head enters a photographic picture plane, so that a film surface, especially in a picture plane might be damaged. Also, in the magnetic head described in Japanese Patent Laid Open No. 3-200131/1991, because the magnetic head is operated to touch or not touch film, a film surface might be damaged with the operation.